I have a Rem 700 .300 Win Mag, and I am hoping someone can help me identify a marking on the rifle. The Date Code stamp is OY, (which makes it a manuf. date of 1974), immediatley stamped after the code are the numbers 91. It appears this "91" stamp was put there after the factory stamp at some point. Could this be a stamp put there by Remington, say, had the rifle been sent back for a repair? Anyone can help, I would appreciate it.